The wiggle room in the nozzle is probably common in WE's gbb designs. Both my brand new Scar-L and AKSUN had it from the beginning. It did not affect accuracy or reliability. Never saw an alignment problem in either one though. I tried a R.A-tech barrel and nineball bucking in scar with very good results. In the AK I used the maple leaf crazy jet inner barrel and autobot bucking. The results were excellent both in range and accuracy. They shoot 420fps with 0,20gr bb's. I use 0,30gr bb's in both guns.

 

? how can you check alignment with the bolt pulled back?...

Anyway, a little wiggle between the nozzle and bolt carrier is OK.

Alignment between the nozzle halves can cause issues, but if that's the case, a little teflon tape in the coupling will do the trick.


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Most important stuff for a GBBR is seal between the gas routing parts. So make sure that:

- magazines have no wobble in the magwell. If they do, use tape on the inner walls

- gas routes are in good shape

- nozzle to bolt carrier has good compression. To test this, pull the nozzle out and press it back in while plugin the gas input and output holes, you should feel piston-like compression. If you don't, consider replacing the oring that seals between the piston and the nozzle.

- nozzle to hop unit has good seal. When you pull back the bolt carrier, the nozzle should stick to the chamber for as long as possible before snapping back. If it's going back with the carrier (as most do), a tighter sealing bucking is the way.

All in all, just shimming the magwell and the nozzle halves if needed, and tossing in Autobot bucking so it grabs onto the nozzle is enough. This is extremely important and something most GBBRs fail at, and greatly affects consistency and cooldown resistance (and therefore, accuracy and range)
I would definitely recommend the Crazy Jet barrel to go with it, of course.

As for maintenance, don't go crazy about it. All you really need to do is lube the bolt carrier to nozzle oring once a month or so with a very light silicone oil, and use dry gas to prevent the inner barrel and bucking from being coated with lubricant (this is also extremely common issue, and the biggest cause for inaccuracy in GBBRs) and / or clean the barrel much more frequently than you would in an AEG or springer.

 

Alignment between the bucking and nozzle is what I was referring to. I checked it by pulling the bolt halfway back and seeing if it still lined up with the barrel, which it doesn't by a tiny bit. In the forward position, the bucking lips and rest of the hop up unit/magazine/gasket appear to guide the nozzle into the correct position. It just isn't really lined up perfectly in a rearward position. It seems like I don't need to be worried about this stuff though, so that's good.

 

Quick update as of this morning. Swapped my autobot out of my pistol and put it into the L85. Tried a concave nub in it, and while it did fit and fire, the concave nub is a bit too large and causes pre-engagement with the rubber. It's overhopping everything with the hop up turned all the way down. Despite the overhop, the horizontal spread is significantly lower than the original bucking (as expected).

Swapped the nub back to the normal bar style nub, and the overhop issue is gone. Horizontal spread has worsened a little bit, but is still much better than what it used to be. With the minimal testing I've been able to squeeze into this morning, the performance is much more usable. So far, no significant fliers like those I used to get, so lets hope it stays that way. Didn't chrono since I didn't have much time.

As a side question, will changing the output pressure of my regulator impact the cycle speed of my rifle? It's shooting a little bit hot for the field, and I'll have to turn it down a bit in order to have it running at a field legal velocity...

 

Changing pressure should affect mostly the felt recoil and RoF, without changing the FPS much, because of the floating valve. My WE (custom made) RPK shoots the exact same 423FPS at 80 PSI all the way up to 160PSI.

 

Hmm, looks like I'll have to run a barrel swap then. Think I was running around 375 fps with 0.3's the last time I checked, but that was with the old bucking. It's probably higher now with the autobot bucking. I know I have a 280mm crazy jet laying around, but I feel like that might drop it down too much. I suppose I have to play the guessing game now heh

 

I'd definitely go with the Crazy Jet, Autobot and regular nub. And get a chrono

 

Ah, I have a chrono, just didn't take it out into the backyard. I only had a few minutes to test in the morning before work and I typically get back after its dark :\

Edit: Kinda regret not chronoing earlier. I'm actually at 475 fps with 0.3g bb's at 100 psi...

Edit 2:
510mm 6.01 Unknown Inner Barrel @100 PSI, maple leaf autobot 70: 475 FPS
280mm 6.04 Crazy Jet Barrel @100 PSI, maple leaf autobot 70: 380 FPS